Outstanding grass green crystals of the extremely rare mineral vajdakite from the type and only known locality worldwide: Jachymov (St Joachimsthal), Bohemia, Czech Republic. Vajdakite is a molybdenum arsenite. — Photo: David Hospital · CC BY-SA 4.0
Vajdakite
Vajdakite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula (Mo⁶⁺O₂)₂As³⁺₂O₅·3H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/c).
Key properties: specific gravity 3.5; White to light gray-green streak; Vitreous luster; optically biaxial.
IMA symbol Vaj, IMA status: approved, named in 1998.
Found as a rare secondary mineral in a highly oxidized uraninite-arsenide-sulfarsenide deposit (Czech Republic).
It is found associated with Arsenolite, scorodite, parascorodite, kaňkite, annabergite, köttigite, pyrite, marcasite, nickelskutterudite, löllingite.
The mineral was named to honor Josef Vadjak (b. 1930), of Pequa Rare Minerals, Massapequa, New York, USA, who drew attention to the species.